Paper storage device

Abstract

A paper storage device comprises a sensor for generating a detection signal indicative of the arrival of a top level of a stack of papers on a paper support tray at a predetermined height so that the paper support tray can be lowered in response to the detection signal, and a counter for counting the number of papers successively stacked on the paper support tray so that an indication that the paper support tray is held at an improper position can be provided when the counter counts a predetermined number of the papers during the absence of the detection signal from the sensor. Once the top level of the paper stack on the paper support tray has attained the uppermost limit position, the top level of the paper stack on the paper support tray is lowered to a lowermost limit position to secure the orderly disposition.

What is claimed is: 
     
       1. A paper storage device for receiving recording papers successively discharged from an image forming apparatus and for accommodating the recording papers in a stacked fashion, which comprises: a tray for accommodating the recording papers;   a drive means for driving the tray up and down;   means for detecting an arrival of a top face of the recording papers on the tray at a predetermined height;   a control means for lowering the tray on the basis of an output from the detecting means;   means for counting the number of the recording papers delivered onto the lowered tray from the image forming apparatus; and   means for determining that a position of the tray is improper when the number of the recording papers counted by the counting means reaches a predetermined value and the top face of the recording papers on the tray has not yet reached the predetermined height.   
     
     
       2. The paper storage device as claimed in claim 1, further comprising a second determining means for determining the type of each of said recording papers and means and for changing the predetermined value of the number of recording papers on the basis of a result of a decision made by said second determining means. 
     
     
       3. The paper storage device as claimed in claim 1, further comprising means for elevating the tray when the determining means determines that the position of the tray is improper. 
     
     
       4. The paper storage device as claimed in claim 1, further comprising means for issuing a warning in the event that the position of the tray is determined improper. 
     
     
       5. The paper storage device as claimed in claim 1, further comprising means for determining the absence or presence of the recording papers on the tray and a control means for elevating the tray to the predetermined height in the event of the absence of the recording papers on the tray. 
     
     
       6. The paper storage device as claimed in claim 1, wherein said control means for lowering the tray terminates a lowering operation at a timing when an output from the detecting means is OFF. 
     
     
       7. A paper storage device for receiving recording papers successively discharged from an image apparatus through a discharge opening and for accommodating the recording papers in a stacked fashion, which comprises: a tray for accommodating the recording papers;   a drive means for driving the tray up and down relative to the discharge open of the image forming apparatus;   means for detecting an excess of a top face of the recording papers on the tray over a predetermined position defined below the discharge mouth;   a control means for controlling said drive means to lower said tray until the top face of the recording papers on the tray is lowered below the predetermined position;   means for counting the number of the recording papers delivered onto the lowered tray from the image forming apparatus through the discharge opening;   a reset means for resetting a count of the counting means when the detecting means detects the excess of the top face of the recording papers on the tray over the predetermined position; and   means for determining that a position of the tray is improper when the number of the recording papers counted by the counting means reaches a predetermined value.   
     
     
       8. The paper storage device as claimed in claim 7, further comprising a second means for controlling the drive means so a to elevate the tray when said determining means determines that the position of the tray is improper. 
     
     
       9. The paper storage device as claimed in claim 8, wherein said second control means brings the drive means to a halt when the detecting means detects the excess of the top face of the recording papers on the tray over the predetermined position.